1980 Evinrude 100HP running erratic - newly rebuilt

[dicarlo]

My 1980 Evinrude 100HP is suddenly not running right. rebuilt the whole powerhead last year, with carbs and also replaced the power packs this past summer. New plugs this month as well.

It fires up and idle seems to be okay but when I get on it it seems like its misfiring or running on not all cylinders. Almost the same feeling when one of the power packs went bad. Being that the power packs are both new, I am inclined to believe that they are not bad again. Seems like definitely some sort of ignition issue though. Plugs and wires are brand new. Could this be a coil? Last time I took it out it would run fine at WOT and then suddenly start cutting in and out (loosing power and then taking off again.) By time I got back to the dock it seemed to be worse. But it does seem sporadic. How can I test the coils if this is a possible issue?

thanks guys.

 

[racerone]

The term " newly rebuilt " does not mean much to me.------What was done to the motor , as rebuilt means different things to some folks.------Use a timing light on it to see if you can pinpoint the cylinder with the miss.

 

[dicarlo]

Let me clarify, newly rebuilt - new pistons, rods, bearings, ect. basically a new powerhead when it was all said and done.

 

[emdsapmgr]

Not unusual for older ignition components to act up once the engine heats up to normal operating temps. May run fine when cold, crappy when it's warmed up. Even new power packs will misfire if they don't get enough voltage. Check your stator output. At normal cranking rpm's (minimum 250) , you should see a minimum of 150 volts as measured on a special "peak reading" voltmeter. If the voltage is lower, it won't be enough to fire every plug during every crank rotation. Test is best when the engine is warmed up. While testing, might as well check the cranking voltage output on the timer base. Should be something like 0.3 volts on a V4. The four coils can fail individually, but are usually considered the most reliable ignition system component. You can find specific ignition troubleshooting specs for your exact engine at this excellent website: cdielectronics.com

 

[pn]

did u rebuild your fuel pump when you did the power head rebuild? fuel lines, just something to take a peek into if you have spark.

 

[dicarlo]

did u rebuild your fuel pump when you did the power head rebuild? fuel lines, just something to take a peek into if you have spark.

Yes I did. Carb kit, fuel pump rebuild and new lines...

 

[dicarlo]

Not unusual for older ignition components to act up once the engine heats up to normal operating temps. May run fine when cold, crappy when it's warmed up. Even new power packs will misfire if they don't get enough voltage. Check your stator output. At normal cranking rpm's (minimum 250) , you should see a minimum of 150 volts as measured on a special "peak reading" voltmeter. If the voltage is lower, it won't be enough to fire every plug during every crank rotation. Test is best when the engine is warmed up. While testing, might as well check the cranking voltage output on the timer base. Should be something like 0.3 volts on a V4. The four coils can fail individually, but are usually considered the most reliable ignition system component. You can find specific ignition troubleshooting specs for your exact engine at this excellent website: cdielectronics.com

Getting proper voltage from stator when tested. 200 volts. How can I test the coils? And power packs (although assuming they are good since new) Thanks

 

[racerone]

Use a timing light to see if you can pinpoint the cylinder with the miss.------Run with a known to be good fuel tank and hose to see if fuel supply might be a problem.

 

[Bosunsmate]

Check all your plugs, any a different colour?

 

[emdsapmgr]

If you think the ignition is ok, then do this simple fuel test: When the engine is running and starts performing poorly, have a buddy constantly prime the fuel hose bulb. This will force extra fuel into the carbs. If it runs ok as long as you constantly prime the fuel hose bulb, you've got a fuel delivery problem. Weak pump, restricted hose, bad fuel primer bulb, sticking anti-siphon valve on the fuel tank, bad fuel connection (getting air in the line) etc.

 

[dicarlo]

If you think the ignition is ok, then do this simple fuel test: When the engine is running and starts performing poorly, have a buddy constantly prime the fuel hose bulb. This will force extra fuel into the carbs. If it runs ok as long as you constantly prime the fuel hose bulb, you've got a fuel delivery problem. Weak pump, restricted hose, bad fuel primer bulb, sticking anti-siphon valve on the fuel tank, bad fuel connection (getting air in the line) etc.

After some more testing I realize that I misread my voltmeter on the previous test / post. I am getting ONLY 20 VOLTS from the stator when running at 3500RPMs (from the 2 yellow wires from the stator.) Not 200 volts. This is all being done in a water can and not on the lake (although don't think that will make a difference for whats going on.) Any ideas?

 

[emdsapmgr]

20 volts is nowhere near the minimum of 150....re-read comment #4.

 

[dicarlo]

20 volts is nowhere near the minimum of 150....re-read comment #4.

Am I correct in testing the voltage from the 2 yellow wires the come out from under the flywheel, I believe thats the wires from that stator.

 

[racerone]

Yellow wires have to do with battery charging.----That function is seperate from the electronics to make the spark for ignition.

 

[ondarvr]

It is very common for coils to fail at higher RPM's or when they get hot.

 

[emdsapmgr]

The CDI trouble shooting guide indicates the ignition voltage is measured between two wires at the connector: the brown and brown wire with yellow stripe. You've got two packs, so you should have two connectors to test between the A and B terminals. Measure the output between both terminals. Must be between 150 and 400 volts.

 

[dicarlo]

The CDI trouble shooting guide indicates the ignition voltage is measured between two wires at the connector: the brown and brown wire with yellow stripe. You've got two packs, so you should have two connectors to test between the A and B terminals. Measure the output between both terminals. Must be between 150 and 400 volts.

Thanks for all the info. Finally had a chance to get back to work on my boat. It ended up being a bad coil on one of the cylinders. Running strong now. 43mph on the water today! Ya!